Layout · Gru docs

Short author rules for height, scroll, and the composition stack. Name the mode before you fight bounds.

One job per layer

Document.Root → shell → (grid) → (Viewport) → Panel/Card → widgets

Overlays (modals, dropdowns) draw above the tree and must not change sibling layout extent.

Mode	Meaning
Intrinsic	Shrink-wrap content at assigned width
Fill	Consume remaining main-axis space (`FlexGrow`)
Fixed	Exact height band

Pick one per node. Measure width-first. Never leave probe/measure heights as final bounds.

Need	Use
Page scrolls as a document	One page-scroll `Viewport` in the shell body
Pane fills remaining height	`FlexGrow` fill child (optional nested Viewport)
Modal	Flat flex body only — not a Viewport root